Protective coatings for iron and steel



United States Patent 2,927,089 PROTECTIVE COATINGS FOR IRON STEEL HowardN. Copthorne, Fort Lauderdale, Fla.

No Drawing. Application May 33,, 1957 SerialNo. 662,592.

5 Claims. "(CL 260-19) This invention relates to protective coatings foriron and steel, and more particularly to protective coatings which do:not form a skin and have a hard surface.

In the usualrust-inhibitive primers, the pigments are incorporatedinvehicles which dry to produce a somewhat elastic skin, binding theparticles of the pigment together. When corrosive elements which may bepresent on the metal, surface or moisture contaminated with chemicalsfrom the atmosphere pass through or under the skin,

rusting action spreads beneath the skin causing it to eventually'peel'ofi exposing the rusted surface that has been hidden beneath theskinbefore the actual peeling occurs. The period of time in whichprimers form a protective coating before deterioration of themetal'surfacersets in, and tovyhat extent the primers are protective,dependsupon many factors, such as the preparation of thesurface'to betreated, the number .o fcoats of primer applied, and the location of thesurface to be treated. In order to eliminate the inherent defects ofskinforming primers, a plastic primer-wasdeve'loped, disclosed in UnitedStatesPatent No. 2,609,302. However, primers that form a plasticnon-skin-for-ming coating on the surface to beuprotected donot meet allthe goals of an ideal protective coating. First of all, the plasticprimers are notcompletely resistant to direct corrosion in chemicals.Also, the plastic primers do not have a surface condition suitable forfurther coatings of all types. Instead, the

plastic primer remains soft andpliable. While the latter is an advantageover skin-forming primers, because it disallows the corrosion fromspreading, yet it is desirable to have an outer surface of a hardmaterial for many applications, A hard outer surface is moreabrasion-resisting than a soft one. Also, if the outer surface isadditionally porous it is a good foundation for other protectivecoatings, such as the vinyl plastics, oleoresinous, and oil paintsgetc.Varnish alone added to the rust resistant composition of fatty acids,sulfur, and litharge disclosed in Patent No. 2,609,302 does not producethe desired hard surface. Furthermore, varnish is not completelycompatible with such a composition.

It is, therefore, an object of the present invention to provide aprotective coating adapted to be applied to the surface of iron or steelmenrhersh'aving all theadvantages of a plastic non-skin-forming primer,and which also has a surface condition suitable for further coatings ofall yp It is a further object of the invention to provide protectivecoatings for "iron and steel having a soft plastic undercoating with aharder coating over the primer.

It is a yet "further object of the invention to provide protectivecoating of a plastic primer and a layer that presents a porous surfaceto which maybe applied further layers of plastics or other paints. I

It is another object of the invention to provide protective coatingsthat do not'support combustion.

It is a still further object of the invention to provide a composition"for iron and steel that is water resistant.

It is yet another object of the invention to provide a thick and yetinexpensive protective coating for iron and steel members.

Patented Mar. 1, 1960 Broadly stated, the present invention relates to acomposition containing the reaction product of a fatty acid, sulfurandlitharge; calcined gypsum, and a varnish.

It was discovered that a composition of varnish and gypsum, togetherwith a fatty acid, sulfur, and litharge reaction product dries to ahard, somewhat porous surface, and that varnish in such a composition iscompatible.

As previously indicated, one or the components in the composition is thereaction product of a fatty acid, lead oxide, and sulfur. The product isprepared by heating the reaction mixture to elevated temperatures.

The fatty acid is preferably .a monobasic fatty acid containing not lessthan-sixteen carbon atoms and usualiy o o ha e mor han f t erbi s t hexamples of fatty acids that may be used are oleic, linseed oil fattyacid, .soy bean oil fatty acid, tung oil .fatty acid, stearic, linoleic,palmitic, linolic, linolenic, and clupanodonic. Special preferenceis.given to oleic acid. The lead oxide used is preferably in the form oflitharge.

The mixture of fatty acid, lead oxide, and sulfur are reacted attemperatures within the range of 300 F. to 500 F., preferably within therange from about 350 F. to 450 F. Sample preparations may be prepared byusing a fatty acid in the amount of from about to 30%, preferably about47%, lead oxide in the form of litharge, in an amount from about 30% to65%, preferably about 47%; and sulfur in'an amount varying from 2% to10%, preferably about 6%, by weight of the initial mix. For bestresults, it is desirable to have stoich-iometric amounts of lead andsulfur. The reaction is carried on to completion, which u sually occursfrom within about .25 to about .ldhours. During .the reactionperiod thematerials are continuously mixed or stirred, as by a mechanical stirrer.I

After the reaction is completed, the reaction mass is cooled withstirring below 400 F. and a volatile thinner is added in an amount togive the desired consistency to the final preparation while the reactionmass is continuously stirred until the same is cooled to atmospherictemperatures. Such volatile thinner may comprise coal tar solvents, suchas naphtha, xylol, toluol, petroleum solvents, such as mineral spiritsand varnish makers and painters naphtha, turpentine and the like. In thepreferred instance about 47 parts by weight of solvent is added to about53 parts by weight of the reaction mass.

After the reaction is cooled and the volatile thinner added, it isdesirable to allow the mixture to stand for about 12 hours or more, andthen stir with mixer. This additional stirring gives the product a finalconsistency.

The following'examples illustrate preparations which meet therequirements for a plastic primer herein disclosed and show the widerange in which the components may be mixed. Ineach of thefollowingexamples the fatty acid and sulfur'were heated to about 360 F.to 380 F., then .litharge was added and an exothermic reaction resultedwhich raised the temperature to about 410 F. to 450 F.

EXAMPLE 1 Approximate Pounds percent by weight Oleic acid p as Litharge45 30 Sulfur J. 6 4

EXAMPLE 3 Approximate pounds percent by weight Tung oil fatty acid 10047 Litharge 100 47 Sulfur 14 6 EXAMPLE 4 Oleic acid 100 07 Litharge 4530 Sulfur 4 3 EXAMPLE 5 Linseed oil fatty acid 100 47 Litharge 100 47Sulfur 14 6 EXAMPLE 6 Oleic arid 100 59, 5 Litharge 60 35. 5 Sulfur 85.0

EXAMPLE 7 Oleic acid 100 54 Litharge 75 41 Sulfur 10 5 I EXAMPLE 8 Oleici 100 49 Litharge 90 45 Sulfur 12% (5 EXAMPLE 9 Oleic acid 100 61.Litharge 60 36. Sulfur 4 2. 5

EXAMPLE 10 EXAMPLE 12 Oleic acid 100 40 Litharge 130 53 Sulfur 18 7While the number of illustrative examples of the invention are set forthhereinabove, Example 10 has been found particularly desirable as acoating material adapted for many uses. In preparing a final compositionfor application to metal surfaces from the reaction product of Example10, 150 pounds of naphtha is stirred into the heated mass while the sameis cooled to atmospheric temperatures. The reaction product containing40% by weight of thinner may be present in the composition in the rangefrom about 35% to 89% by weight of the total components, or, apart fromthe thinner, in the range from about 20% to 53% by weight of the totalcomponents.

In addition to the reaction product described hereinabove, thecomposition contains calcined gypsum. Ordinarily gypsum crystallizeswith two molecules of water equal to about 21% by weight, andconsequently has the formula CaSO .2H O. The calcined or partiallydehydrated gypsum that is used in the composition has approximately byweight of the water removed and is known in the trade as plaster ofParis. The calcined gypsum is ordinarily employed in the composition inthe range from 10% to 45% by weight.

In addition to calcined gypsum the composition contains a minor amount,usually at least 1% by weight of the total composition of a varnish, forexample, a phenolformaldehyde tung oil varnish. Other varnishes may beemployed in the composition. The varnish may be presentin thecomposition from about 1% to about 20% by weight.

In formulating the composition, the varnish is first added to thereaction product. The gypsum is next added so that the varnish plus thereaction product wets the gypsum and spreads over its surface.

The following examples illustrate the composition of the invention.

EXAMPLE 1s Approximate percent by weight Reaction product of Example 1050 Plaster of Paris 35 Phenol-formaldehyde varnish 15 EXAMPLE 14Reaction product of Example 11 50 Plaster of Paris 35Phenol-formaldehyde varnish 15 EXAMPLE 15 Reaction product of Example 345 Plaster of Paris 40 Phenol-formaldehyde varnish 15 EXAMPLE 16Reaction product of Example 5 35 Plaster of Paris 40 Phenol-formaldehydevarnish 25 1 Containing 40% by weight thinner.

The gypsum and varnish in the composition have a unique cooperativeeffect contributing to the hardness of the outer surface when dried.Also, the coating dries without formation of skin, customary of paintsand primers. The varnish contributes to water resistant properties ofthe dried coating.

In applying the protective coatings of this invention, the iron or steelsurface may be first prepared by wire brushing or sandblasting. Thecomposition is coated over the surface by any of the usual mechanicalmethods, such as spraying, brushing, etc.

The outer surface of the composition is hard upon drying, protecting itagainst removal, as by scraping and abrasion. It also presents a surfacethat is well suited for the application of other protective coatings.Polyvinyl resins, polystyrene resins, as well as conventional paints maybe satisfactorily applied-to the dried coating. In this way a thick,inexpensive protection is given the iron and steel members. Plasticresins, such as polyvinyl or polystyrene resins, which form an effectivecoating against direct chemical attack, have been found especiallysuitable for application to the composition disclosed herein.

Other modes of applying the'principle of the invention may be employed,change being made as re gards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

I, therefore, particularly point out and distinctly claim as myinvention:

1. A protective composition for iron and steel members consistingessentially of about 30% by weight of a reaction product of from about30% to 65% by weight of a fatty acid having not less than sixteen andnot more than forty carbon atoms, from about 30% to 65% by weight oflitharge, and from about 2% to 10% by weight of sulfur; about 35% byweight of calcined gypsum;

about 15% by weight of phenol-formaldehyde varnish; and in addition tothe foregoing components volatile thinner in amounts sufiicient toimpart a consistency for coating said iron and steel members.

2. A protective composition for iron and steel members consistingessentially of from about 21% to 53% by weight of the reaction productof from about 30% to 65% by weight of a fatty acid having not less thansixteen and not more than forty carbon atoms, from about 30% to 65% byweight of litharge, from about 2% to by weight of sulfur ata'temperature from about 300 F. to 500 F.; about 10% to 45% of calcinedgypsum; about 1% to 20%by weight of phenol-formaldehyde varnish; and inaddition to the foregoing components volatile thinner in amountssufiicient to impart a consistency for coating said iron and steelmembers.

3. The composition of claim 2 wherein said fatty acid is oleic acid.

4. The process for producing a rust inhibitive preparation which forms areaction product of from about to 75% by weight of a fatty acid havingnot less than sixteen and not more than forty carbon atoms, about 22% to53% by weight of lead oxide, about 2.5% to 7% by weight of sulfur at atemperature within the range of from about 300 F. to 500 F.; addingvolatile thinner to said reaction product in amounts suificient toimpart the desired consistency to the composition; adding from about 1%to 20% by weight of phenol-formaldehyde varnish; and admixing 10% to byweight of calcined gypsum.

5. The process of claim 4 wherein said fatty acid is oleic acid.

References Cited in the file of this patent UNITED STATES PATENTS 84,421Irish Nov. 24, 1868 1,570,169 Nelson et al I an. 19, 1926 1,763,937Stievater June 17, 1930 2,609,302 Copthorne Sept. 2, 1952

1. A PROTECTIVE COMPOSITION FOR IRON AND STEEL MEMBERS CONSISTINGESSENTIALLY OF ABOUT 30% BY WEIGHT OF A REACTION PRODUCT OF FROM ABOUT30% TO 65% BY WEIGHT OF A FATTY ACID HAVING NOT LESS THAN SIXTEEN ANDNOT MORE THAN FORTY CARBON ATOMS, FROM ABOUT 30% TO 65% BY WEIGHT OFLITHARGE, AND FROM ABUT 2% TO 10% BY WEIGHT OF SULFUR, ABOUT 35% BYWEIGHT OF CALCINED GYPSUM, ABOUT 15% BY WEIGHT OF PHENOL-FORMALDEHYDEVARNISH AND IN ADDITION TO THE FOREGOING COMPONENTS VOLATILE THINNER INAMOUNTS SUFFICIENT TO IMPART A CONSISTENCY FOR COATING SAID IRON ANDSTEEL MEMBERS.